Balance mechanism for instruments



Sept. 22, 1931. J. H. MILLER 4,

BALANCED HECHANISM FOR INSTRUMENTS medua s, 1930 Patented Sept. 22, 1931 UNITED STA rss PATENT OFFICE JOHN H. MILLER, OF OAK PARK, ILLINOIS, ASSIGNOR TO JEWELL ELECTRICAL INSTRU- KENT 00., OF CHICAGO, ILLINOIS, A. CORPORATION OF ILLINOIS BALANCE mncmmsm roa ms'raUmm-rs Application filed may a,

The present invention relates to animproved balance mechanism for instruments, and is particularly concerned with the static balancing of electrical measuring instru- 5 ments. While the mechanism is peculiarly adapted to be utilized for the static balancing of a pointer, it may also be employed upon any other moving parts of instruments or devices in which a static balance may be i desirable.

' Z studs on the moving part, but the amount of frictional engagement which is present in such devices to assure maintenance of the adjustment under vibration, shock or use, renders the adjustment so hard that when an adjustment 1s made, it is very liable to injure the pivots or other parts of the delicate mechanism.-

One of the objects of the present invention is the provision of an improved balance mechanism, by means of which the balance weights are held with suflicient firmness to assure maintenance of proper adjustment, but which is also adapted to permit release of the weights for ready adjustment without the application ofany but the-lightest force, thereby avoiding any possibility of injuring the pivots or other delicate parts. Another object is the provision of an improved balance mechanism for instruments, which does not require the delicate machine work necessitated y the devices of the prior art, but which lends itself readily to manufacture by stamping operations, thereby reducin the cost of labor and machinery require I Another object is the provision of an improved balance mechanism, including releasable balance members which are capable of being secured in any of a multiplicity of positions on the balancing arms of' the move- 1930. Serial, 1'... 45am.

ment, but which do not require the use of excessive force nor special tools for their adustment.

Another object is the'provision of an improved resilient securing device for simple balance weights on the movement of an instrument, which securing device is peculiar ly adapted to have its tension readily adjusted to the pointat which the maintenance of the adjustment is assured, but the force required for making an adjustment is not sufficient to damage the pivots or other parts, and by means of which the weight may be readily released for relatively free movement if the balance weight does not lend itself to ready ad ustment by application of alight force. I

' Other objects and advantages of the invention will be apparent from the following descrlption and from the accompanying drawings, in which similar characters of reference.

indicate similar parts throughout the several views.

Referring to the single sheet of drawings Fig. 1 is an enlarged view in perspective, of the moving element of an electrical instrument of the moving coil type, equipped with a balance mechanism constructed according to the present invention;

Fig. 2 isan enlarged plan view of the pointor and balance mechanism, with the torsion springs and coils removed;

Fig. 3 is an enlarged sectional view through one of he arms of the balance mechanism, taken on the plane of the line -33 of Fig. 2

Fig. 4 is an enlarged sectional view taken on the plane of the'line 44 of Fig. 2;

- Fig. 5 is a detail, sectional View greatly enlarged, taken on the plane of the line 5-5 of Fig. 4; and v Fig.6 is a plan view of one of the supporting elements or plates for the balance weights;

The present balance mechanism may be used upon any t e of moving element, but the typeselected or illustration is the moving coil element of an such as an ammeten The moving coil ele electrical instrument, q

ment comprises a supporting franle 10, which may consist of a relatively short length of light and thin aluminum tube, preferably rectangular in cross section, having outwardly extending flanges 11, 12 at each side, forming a spool for supporting the coils of fine insulated wire 13, such as enameled wire.

, Each end of the spool is provided with a hardened steel pivot 14 formed with a point 15 of. substantially conical formation, and fixedly supported in a hub 16 of aluminum or other light, easily worked metal. The hub 16 is preferably supported upon a securing plate 17 which may be cemented or otherwise permanently secured to the ends of the spool 10 outside the coils 13, so as to secure the pivots "slidably 14 axially upon the moving element.

The hub 16 is provided with an axial bore- 18 and the pivot pin 14 may be secured by a close frictional fit in the bore 18 or by pressing the metal of the hub 16 about the pivot pin- I 14, as described hereinafter. The hub 16 is also preferably formed with an enlar ed portion 19 adjacent the securing plate 1%, forming an annular shoulder 20 for securing the pointer and arms of abalance mechanism to the hub 16 by means of a riveting operation, as described hereinafter.

The balance mechanism for the moving element 10 preferably includes a plurality of symmetrically located balance arms 21, 22,

23, ,which preferably extend substantially radially with respect to the axis of rotation of the moving element 10 and the present balance arms preferably each include at least two resilient members 24, 25, 26, 27, 28, 29 for and releasably securing the balance weights 30, 31, 32.

The balance mechanism is preferably constructed by providing two or more plates 33, 34 of relatively thin and light, yet resilient and hard material, such as spring brass or bronze, each of the plates having a centrally located body 35 which is' preferably round to improve the balance of this element and which is rovided with radially extending arms.

suc as the arms 25, 27, 29 and 36 in Fig. 6; a

The body 35 is provided with a centrally located aperture 37 of suficient size to receive the reduced cylindrical portion 38 of hub 16, and the complete assembly of balance mechanism andpointer may be secured upon hub 16 by rivet formations 39 which press the plates 33-34 against the shoulder 20 of hub 16.- The riveting operation as illustrated, comprises the formation of a pluralityof radially extending lugs 39 on hub 16 above the plates 33, 34, the lugs 39 being pressed out of parts of' the hub 16, and this operation also serving to improve the securement of the pivot pin 14 in the hub 16,

but any convenient form of riveting may be em loyed. I

lthough the present. embodiment shows three radially extending arms 21, 22, 23 symmetrically located with respect to the pointer 1 40, it should be understood that in some embodiments of the invention, only a single balancing-arm might be utilized or a greater number of symmetrically located balancing arms might be employed if a more accurate balance were desired, but the present empresent invention finds its widest field of application to instruments having pointers, such as the pointer 40, which preferably consists of an elongated metal member constructed of relatively light metal, such as aluminum and formed with a head 42.having a point 43 located above the usual scale.

The pointer 40 is preferably formed with a longitudinally extending rib 44 for the purpose of increasing its rigidity and in order to bring the pointer u above a dial and to provide more room be ow the dial for other parts of the instrument, the pointer may be provided with one or more offsets 45. The end of the pointer opposite from point 43 is provided with an aperture 46 adapted to receive the reduced cylindrical part 38 of hub 16, and the pointer is preferably secured between the plates 33, 34, in order that this end of the pointer may perform the additional function of spacing the parts of the arms 21, 22, 23.

The plates 33, 34 of the balance 'mechanism are preferably formed by a stamping operation for the purpose'of decreasing the cost of manufacture of these parts, and in order. that the arms 24 to 29 may be pro.-

' vided with relatively sharp or cutting edges for better securing the balance weights 30 to 32 in adjusted position.

Referring to Fig. 5 showing a section ofone of the balance weights and the parts of one balance arm, it will be observed that the extend in a directionopposite to the burrs on an arm immediately adjacent thereto.

Thus each of the arms 21 to 23 is'formed by a pair of resilient spreading members having relatively sharp cutting edges 47 which tend to cut into the inner wall of the weights 30 to 32.

The weights 30-32 preferably consist of tubular metal members. of relatively soft metal such as aluminum which is capable of being cut at least to some degree by the relatively hard resilient arms 24-29 of spring bronze or brass.

The amount of tension of the respective part of the arms 2123 may be regulated by bending the arms apart so that the parts of each arm, as for instance, 26, 27, resiliently engage the inside of the corresponding tube 32 to hold the tubular weight in any ad usted position. The regulation of the tension may be improved, however, by skewing the respective parts of each arm, that is, bending the arm 27 laterally with respect to the arm 26, thereby increasing the tension of the arms since the arms are more rigid in the plane of their widest dimension as shown in Fig. 5, and it will be evident that the amount of tension of the balance arms may.

be regulated as desired to secure the weights in anyadjusted position without danger of change of the static balance by. vibration, shocks or abuse of the instrument. a

The tension may be so regulated that the weights will move sufliciently easily to allow for adjustment without damaging the pivots or themoving element, but the force required is such that the weight will not move of its own accord under any condition of service.

Furthermore, if necessary, the weights may be released by-simply pressing the resilient parts of each arm together, after which ree movement of the weight is assured, and the adjustment of the weights to secure a static balance may be accomplished without the use of any special tools and without danger of damaging the delicate parts of the instrument,

It will thus be observed that I have 1n- .vented an improved balance mechanism including resilient balance arms for slidably 0r releasably securing balance weights in such manner that an adjustment may be readily efi'ected without possibility of injury to the instrument, and all of the parts of the balance mechanism lend themselves readily to manufacture by ordinar stamping operations or cutting from stoc materials, so that the lpresent device is peculiarly adapted tobe show that there is no difliculty-experienced made at a low cost. The vibration tests and life tests of the present balance mechanism due to the weight moving after originally adjusted, but if any weight should tend to stick during an adjusting operation, 1t may be readily released by a slight pre$ure on the resilient parts of the balance arm;

The present construction greatly reduces the cost of this part of the instrument over the old methods of construction'which. involve the cutting of fine threads on a balance T arm and in a' nut, and the possibility of the balance weight binding upon a balance arm so as tovrequire the use of'excesslve force in effecting an adjustment is also eliminated. 1

While I have illustrated a preferred em; bodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the ap ment, a balance mechanism comprising an outwardly projecting arm includmg a plurality of resilient members, and a balance weight carried by said resilient members and frictionally engaged thereby.

- 2. A balance mechanism comprising a a pair of resilient sheet metal arms pointer, spaced from each other by said pointer, and a metal member slidably and releasably en gaged by said resilient metal arms for-improvin the balance of said pointer, said arms extending at a slight angle with respect to each other to increase the tension of said arms. I

3. A balance mechanism for instruments, comprising a moving element, a hub carried thereby and having a shoulder for engaging a pointer assembly, a pointer, and a pair of resilient metal arms mounted on said hub and confined against said shoulder by rivet formations on said hub, and a metal balance member slidably mounted on said metal arms, said arms having outwardly turned burred corners and said metal member comprising a tubular memberof softer metal than said arms.

4. A balance mechanism for instruments, comprising a moving element, a' hub carried thereby and having a shoulder for engaging a pointer assembly, a pointer, a pair of-replurality of symmetrically arranged arms, arranged on said hub on opposite sides of said pointer and spaced from each other by said pointer, and tubular soft metal members slidably mounted on said arms and resiliently. 115

engaged thereby, the arms of eachmember extending at a slight anglewith respect to the adjacent arm said arms, said'arms having burred edges turned outward to engage said tubular inenifor improving the balance of said pointer.

6. A balanced mechanism comprising a- 'silient sheet metal members, each having a to increase the tension of pointer and metal plate formed with an annular shoulder and a hub, a pointer carried by said hub, a pair of resilient metal members of cruciform shape located on said hub and s aced from each other by said pointer, and tu ular metal members on each of the arms of said cruciform members, said tubular members comprising balance weights releasably and slidably engaged by the arms of said cruciform members when said cruciform members are sprung apart. 4

In witness whereof, I hereunto subscribe my name this 2nd day of May, 1930.

JOHN MILLER. 

